the canvas does not automatically resizes, when its parent-div got resized.
I have seen in the source-code, that the canvas resizes when the window-size is changed.

Automatically checking if parent-div has changed seems to be quite complicated, but if you could put the listener function to public, this would be nice.
So we could trigger it by hand, and take the responsibility, if its called to often.

In the latest version you can just call render method whenever its container’s size changes and the chart readjusts its size (only if required) and also redraws the chart to fit the new size. You can also explicitly set width and height (in pixels) of chart in chart options and call render method to update its size.